A new method for modeling large flexible structures

Abstract

The emergence of electronic flight-control systems into commercial aircraft designs has precipitated an immediate need for nonlinear, discrete-time analyses in both frequency and time-domains, for both the aircraft Structural Dynamic Loads and the Flight Controls communities. This paper presents and demonstrates a methodology by which the large-scale, linear aircraft structural models produced by the Structural Dynamic Loads community can be easily reformulated using EASY5x*. EASY5x then provides an environment for incorporating nonlinearities and discretization; and moreover, it provides an intuitive and tractable environment for engineers who are not well versed in linear analysis techniques to manipulate and analyze both the plant and its interactions with a nonlinear, discrete-time control system. The paper then goes on to present a method for transforming the large- scale linear plant into the z-domain using EASY5x. The resulting state-transition matrices propagate the exact solution to structural model equations of motion so simulation accuracy is greatly increased while run-time for statistically significant simulated time intervals is dramatically reduced. Furthermore, the analysis is brought into the efficient, graphically driven environment of the engineering workstation.